Wegovy injection: what to expect when you use the semaglutide pen

Your first injection: what the moment actually looks like

Picture a Tuesday evening. You've taken the pen out of the fridge about half an hour earlier (room temperature makes the injection more comfortable) and you've read through the instructions that came with it. The pen is pre-filled and pre-set; there is no cartridge to load and no dose to dial. You choose a spot on your abdomen, a couple of centimetres away from your navel, and clean the skin. The needle is short and thin. Most people describe the sensation as a mild pinch, nothing more.

You place the pen flat against the skin, press the button, and hold it in place for the count the leaflet specifies, this ensures the full dose is delivered before you withdraw. That's the whole process. The used pen then goes into a sharps disposal container; a 1-litre sharps bin fits neatly in a bathroom cabinet and is the safe, legal way to dispose of used pens at home.

The NHS provides detailed guidance on technique in its semaglutide patient information pages. Read those alongside the leaflet inside your box, and if you would like a step-by-step walkthrough of how to use the Wegovy injection correctly, that guide covers each stage of the process in plain language. If anything in the instructions feels unclear, your prescriber or pharmacist can walk you through it; our support team is available seven days a week.

Which site to use, and why rotating matters for Wegovy injections

Three sites are licensed for the Wegovy injection: the abdomen, the front or outer thigh, and the upper arm. All three reach the subcutaneous fat layer the medicine needs. The reason you rotate (ideally tracking where you injected last week) is straightforward: injecting repeatedly into exactly the same spot can create small areas of thickened or hardened tissue, known as lipohypertrophy. Medicine absorbed through affected tissue may behave unpredictably.

A simple mental map helps. Many people split the abdomen into quadrants and cycle through them; others alternate left thigh, right thigh, left arm, right arm. The exact pattern matters less than the principle: give each site a week's rest before returning to it. More detail on choosing and preparing injection sites covers this systematically if you want a structured approach.

The upper arm is a useful option when the abdomen feels tender or when you're injecting away from home, though it is slightly harder to reach yourself. Some people ask a partner to help with Wegovy arm injections, and having a second pair of hands can make the angle much more manageable. Using the non-dominant arm makes it more manageable solo. If you develop persistent redness, swelling or firmness at any site, mention it to your prescriber at your next review.

How Wegovy's dose schedule shapes your experience over the first weeks

Semaglutide's titration schedule exists because a slower climb lets your body adjust before the appetite-suppressing effects fully arrive. The licensed UK pathway runs from 0.25 mg through 0.5 mg, 1.0 mg and 1.7 mg to the 2.4 mg maintenance dose, each step spaced roughly four weeks apart, at your prescriber's direction. With the MHRA's 2026 approval of a 7.2 mg single-dose pen, some patients may continue escalating beyond 2.4 mg; that is a clinical decision, not one to make independently.

For most people, the early weeks bring noticeable changes in appetite and, for some, nausea after injection day. These effects typically settle within days to two weeks at a given dose. Staying well hydrated, eating smaller meals and avoiding high-fat foods on injection day can all help. The full Wegovy overview sets out what the clinical trial programme found about tolerability at each stage.

If you are considering how Wegovy compares to tirzepatide (Mounjaro), which works on two gut-hormone pathways rather than one, a summary of the available licensed weight-loss treatments lays out the differences clearly. Both are prescription-only medicines; a prescriber weighs your health history before recommending either. STEP 1, the pivotal 68-week clinical trial published in the New England Journal of Medicine, reported an average body-weight reduction of around 15% on semaglutide 2.4 mg, though individual results vary.

Side effects that warrant a call, and the Yellow Card system

Most side effects from Wegovy injections are gastrointestinal: nausea, loose stools, constipation, indigestion. They tend to cluster in the first few days after each injection, especially after a dose increase, and generally ease as the weeks pass. Fatigue, mild headache and dizziness also appear in the trial data.

Some symptoms need prompt medical attention. Severe, persistent abdominal pain that radiates towards the back (with or without vomiting) should not be waited out; it can indicate acute pancreatitis, which the MHRA highlighted as a known but infrequent risk in a Drug Safety Update for GLP-1 medicines issued in January 2026. Signs of a serious allergic reaction (facial swelling, breathing difficulty, rapid rash) also need emergency help.

The UK has a formal reporting system for suspected side effects from any medicine: the MHRA Yellow Card scheme. You do not need a doctor to file a report; patients can do so directly. It is a genuine public health contribution, not a bureaucratic formality. If you have questions about a symptom and are uncertain whether it needs urgent care, our FAQs cover common concerns, and our aftercare team is reachable seven days a week. For anything that feels urgent, contact 111 or your GP.